function delete_old_post_revisions() {
    global $wpdb;

    // Delete post revisions older than 3 months.
    $wpdb->query("
        DELETE FROM {$wpdb->posts}
        WHERE post_type = 'revision'
        AND post_date < NOW() - INTERVAL 3 MONTH
    ");
}

// Schedule the event if it’s not already scheduled.
if (!wp_next_scheduled('delete_old_post_revisions_hook')) {
    wp_schedule_event(time(), 'weekly', 'delete_old_post_revisions_hook');
}

add_action('delete_old_post_revisions_hook', 'delete_old_post_revisions');

// Clear the event on plugin/theme deactivation.
register_deactivation_hook(__FILE__, function () {
    wp_clear_scheduled_hook('delete_old_post_revisions_hook');
});